1. Field of the Invention
This invention relates to wide scan oscillographic recording apparatus.
2. Description of the Prior Art
Oscillographic devices suitable for wide scan recording are known in the prior art. Typically, the recording media are light or heat sensitive, or depend upon the formation of electrostatic charges on the medium. The marking means may include cathode ray pin type and other similar recording tubes. An example of a line scan type oscillographic recording apparatus is shown in U.S. Pat. No. 3,434,158 in which a cathode ray tube having a fiber-optics face is used to produce an electron beam having a predominant wave length which strikes a recording medium that is ultrasensitive to that wave length. The recording medium is moved transversely of the fiber-optics face while the cathode ray tube electron beam is deflected in responsive to an input signal to be recorded. Exposure of the recording medium to the radiation from the electron beam forms a recording trace thereon. Such apparatus provides high speed continuous recording of input signals which may be high or low in frequency and which immediately become visible upon the recording medium.
A disadvantage of such prior oscillographic recorders, particularly where wide scan recording, for example, in excess of 5 inches, is desired is the cost and structural weakness of the large size fiber-optics cathode ray tube that is required, and the cost also the attendant power supply and insulation needed.
An alternative to such wide scan oscillographic recorders is shown in U.S. Pat. No. 3,289,196, Hull, in which two normally blanked fiber-optic cathode ray tubes are positioned side by side and are selectively unblanked for recording on adjacent portions of the same recording medium. The cathode ray tubes are horizontally slaved in a manner such that their electron beams are successively swept, in sequence, across the recording medium. This action closely simulates the operation of a single cathode ray tube of substantially larger size. This result is achieved without requiring the use of large, structurally weak, and expensive recording tubes and the expensive high voltage power supply and insulation needed for such large size tubes.
While effective for the purpose, the side by side cathode ray tube arrangement has left something to be desired from the standpoint of initial calibration of the apparatus, specifically the accurate positioning of the line scan between the two fiber-optic cathode tubes. This calibration adjustment has required viewing the cathode ray tube displays while effecting the necessary adjustments of the associated electronic circuitry. Since the recording medium covers the faceplate and fiber-optics strips of the cathode ray tubes when the apparatus is set up for recording, this has precluded checking the alignment of the line scan between the plurality of fiber-optics cathode ray tubes just prior to effecting a recording operation.
Further, the above-noted Hull patent is directed to the display and recording of alphanumeric characters across the face of the two tubes or alphanumerics on one tube and a related analog trace on the other tube. Thus, another shortcoming of the known prior art is the recognition of a need for a skew correction which carries over from one tube to the other to correct for the skew which would be incident to the continuous movement of the recording medium while the trace is being effected.